i6 



SCIENCE. 



[Vol. XX. No. 492 



THE NUMBER OF BROODS OF THE IMPORTED 

 ELM-LEAF BEETLE. 



BY C. T. EILBT. 



At the meeting of the Entomological Club of the A. A. A. S. 

 in Washington last autumn, Professor John B. Smith, it 

 •will be remembered, gave some interesting observations on 

 this beetle, made at New Brunswick, N.J. As the some- 

 what astonishing result of his observations, he stated that 

 there was but one annual generation, and that the beetles 

 actually went into hibernating quarters early in August. 

 Professor Smith's statements were so emphatic, and evidently 

 based on such careful observations, that they could not very 

 well be gainsaid, but as they conflicted with my observations 

 on the species in the latitude of Washington, for which I 

 have recorded two generations, and exceptionally a third, 

 I was anxious the present season to go over the ground 

 again, still more carefully than in the past, and, by rearing 

 in confinement the first generation of larvae from the first 

 ■eggs hatched, to thus verify, in a manner which could leave 

 eo possible doubt, the facts which I had previously recorded. 

 In this brief note, I desire simply to state that at the present 

 time (June 30) I have eggs laid by the second brood of 

 beetles, i.e., the beetles obtained from larvae which were 

 feeding during the month of May and early part of June, 

 thus proving, in the most positive manner, that in the latitude 

 of Washington there are at least two broods, and that the 

 second brood of larvae will be feeding during July. 



The following from the Appendix to the second edition of 

 Bulletin 6, Division of Entomology, Department of Agricul- 

 ture, October, 1891, will bear repeating in this connection: — 

 " One statement in the life-history of the Imported Elm- 

 Leaf Beetle, as given in the preceding pages, may have to 

 be corrected in the light of the observations of the past six 

 years, and that is in reference to the number of annual gen- 

 erations. Like other leaf-beetles, this insect occupies an 

 extended time in oviposition. The eggs appear to develop 

 slowly in the ovai'ies, and a single female will deposit a 

 number of the characteristic little yellow batches. Tbis fact, 

 taken in connection with the retardation of certain individ- 

 uals of a generation, results in an inextricable confusion of 

 broods. Adult beetles, pupae, larvae in all stages, and eggs, 

 will be found upon trees at the same time, in Washington, 

 during the months of June, July, August, and even later. 

 From this fact it is almost impossible to estimate the num- 

 ber of annual generations without the most careful breeding- 

 cage experiments. There is no evidence that the facts upon 

 record are based upon such careful experiments. Glover, 

 in the annual report of this department for 1867, page 62, 

 says : ' After becoming pupae, in a few days the skin of the 

 back splits open and the perfect insect crawls forth, furnished 

 with wings, by means of which it is enabled to fly to other 

 trees and deposit its eggs, thus spreading the nuisance to 

 every elm in the neighborhood; or it may ascend some tree 

 and lay the eggs for a second generation, which destroys 

 the second crop of leaves, frequently so enfeebling or ex- 

 hausting the tree that it is unable to recover and eventually 

 perishes.' Again, in the Annual Report for 1870, page 73, 

 he says: 'The perfect beetles appear in a few days and im- 

 mediately fly up into the tree to lay their eggs for a second 

 generation, which frequently destroys every leaf on the 

 tree.' 



"The European records seem strangely silent upon this 

 point. In the articles by Leinweber and Frauenfeld, referred 

 to upon page 6, there is no indication of the number of gen- 



erations, but it may be inferred that only one, namely, that 

 of June and July, has been under observation. Heeger, 

 however {loc. cit., p. 114), says that ' under favorable cir- 

 cumstances there are three to four generations during the 

 whole summer. Toward the end of August the insect ceases 

 feeding and retires — partly as larvae and partly as beetles — 

 to winter rest under fallen leaves, in the cracks of bark, 

 holes in the trunks of the trees, and in the ground itself.' 

 This observation was made near Vienna. 



"Our statement upon page 8 was a general one, based upon. 

 the observations in August. This state of aflfairs may proba- 

 bly hold in more northern regions, but in Washington it is 

 safe to say that there are two generations, because, as just 

 stated, newly developed beetles (the progeny of those which 

 hibernate) appear in early June. These lay eggs, and, in 

 fact, egg-laying may continue until the end of September, 

 and larvEe have actually been found by Mr. Pergande iu 

 October." 



THE REPTILIAN RATTLE. 



BY S. GAKMAN. 



Among the specimens secured by Dr. Georg Baur, in his 

 explorations of the Galapagos Islands, there are a number of 

 large lizards of the genera Conolophus and Amblyrhynchus, 

 which exhibit certain peculiarities in the spines of the dorsal 

 crest. Externally each of the spines resembles the rattle of 

 a small rattlesnake. The likeness was evidently brought 

 about by causes similar to those through which the rattle 

 was originated. In a measure, these spines confirm my state- 

 ment of the evolution of that organ as published in 1888 

 (Bull. Mus. Comp. Zool., viii., 259). Figures 1-4, herewith, 

 represent a couple of the nuchal spines in a lateral aspect 

 and views, side and front, of one of the dorsal spines of the 

 Galapagos lizard, Conolophus subcristatus. On making a 

 longitudinal section of any of these spines they are seen to 

 be wholly dermal and to contain neither bones nor muscles. 

 Their epiderm is a little thicker than that of the scales on 

 the flanks. It is apparent that for a time, after hatching, 

 growth of the skin was rapid and regular. The spines de- 

 veloped during this period were subpyramidal ; they tapered 

 so much, on back as on neck, that the slough came off 

 readily and was lost. A periodic growth was taken on in 

 later stages, and, the spines having become more elongate, a 

 slight constriction was formed around the base, from folding 

 the skin by bending the spine from side to side. Becoming 

 still more elongate, the foldings meanwhile increasing in 

 extent and depth, a stage was finally reached which, may- 

 hap aided by shrinkage, retained the epiderm of the spine in 

 place as a cap after the general slough was cast. Thus one 

 thickness after another was added to the covering of the 

 spine, each of the older being shoved farther up, by growth, 

 so as to expose below it a band of the newer cuticle. The 

 folded lower edge, the collar, of the cap rested in a basal 

 groove or furrow, and prevented displacement. Each cap 

 was closely applied to that beneath it, and the spine as a 

 whole was solid. Outwardly the spines resemble rattles; 

 internally the caps rest one upon another too closely to 

 rattle. 



The tip of the tail of the common snake ends in a spine 

 somewhat like that in the crest of the lizard. It differs in 

 containing a bone, the end of the vertebral column. Slough- 

 ing is similar in the two cases, a slight variation only being 

 induced on account of the included vertebra. On most 

 snakes the spine tapers greatly, and the cap is carried off in 



